Let's divide 399418 by 12
We're looking to find how many times 12 goes into 399418.

Going ahead to step 1:
When dividing 3 by 12, we get 0 with a remainder of 3.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Deduct 0 from 3 and we're left with 3.
Append the next digit (9) from the dividend to 3 and continue with: 39 / 12

Moving on to step 2:
12 can be fit into 39 3 times, resulting in a remainder of 3.
Record the quotient 3 as the next digit in the result. 
Result so far: 3.0
Subtracting 36 from 39 leaves us with 3.
Bring next digit (9) of the dividend behind the 3 and repeat the process: 39 / 12

Step 3:
12 can be fit into 39 3 times, resulting in a remainder of 3.
Put 3 as the next digit of the answer. 
Result so far: 33.0
The remainder is 3 after subtracting 36 from 39.
Fetch the next digit (4) from the dividend, attach it to 3 and continue: 34 / 12

Step 4:
If we divide 34 by 12, we get 2 and a remainder of 10.
The next digit of our result is 2. 
Result so far: 332.0
Subtract 24 from 34 to get 10.
Append the next digit (1) from the dividend to 10 and continue with: 101 / 12

Step 5:
When dividing 101 by 12, we get 8 with a remainder of 5.
Record the quotient 8 as the next digit in the result. 
Result so far: 3328.0
If we subtract 96 from 101, we get 5.
Fetch the next digit (8) from the dividend, attach it to 5 and continue: 58 / 12

Going ahead to step 6:
If we divide 58 by 12, we get 4 and a remainder of 10.
Put 4 as the next digit of the answer. 
Result so far: 33284.0
Subtracting 48 from 58 leaves us with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

On to step 7:
When dividing 100 by 12, we get 8 with a remainder of 4.
The number 8 becomes the next digit in our result. 
Result so far: 33284.8
Subtracting 96 from 100 leaves us with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Going ahead to step 8:
12 can be fit into 40 3 times, resulting in a remainder of 4.
Put 3 as the next digit of the answer. 
Result so far: 33284.83
Subtracting 36 from 40 leaves us with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Going ahead to step 9:
40 divided by 12 is 3 with a remainder of 4.
The next digit of our result is 3. 
Result so far: 33284.833
Deduct 36 from 40 and we're left with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

The final outcome is 33284.833, with a leftover of 0.0004.